Temperature compensating fluidic circuit

ABSTRACT

This temperature compensating fluidic circuit has a conventional proportional amplifier which includes an interaction chamber with a beam-forming inlet at one side, spaced outlet passages on the opposite side, opposed control jet nozzles at the sides of the inlet, and passages leading from a common control pressure source to the control jet nozzle. One of these passages contains a restriction of the orifice type and the other contains one or more vortextype resistors. Since the resistance of the vortex-type resistor is due mainly to angular momentum rather than viscosity effects, to which the orrifice-type restriction is particularly responsive, the vortex-type resistor is less affected by temperature change and consequently control signals bearing a predetermined relation to temperature will be applied by the control jets to the fluid beam. A differential pressure output, dependent on temperature will thus be delivered by the amplifier.

Dec# 26, 1972 G. l.. FREDERxcK 3.707,440

TEMPERATURE COMPENSATING FLUIDIC CIRCUIT Filed July 15, 1970 Hrm/elvenUnited States Patent O U.S. Cl. IS7-81.5 8 Claims ABSTRACT OF THEDISCLOSURE This temperature compensating fluidic circuit has aconventional proportional amplifier which includes an interactionchamber with a beam-forming inlet at one side, spaced outlet passages onthe opposite side, opposed control jet nozzles at the sides of theinlet, and passages leading from a common control pressure source to thecontrol jet nozzles. One of these passages contains a restriction of theorifice type and the other contains one or more vortextype resistors.Since the resistance of the vortex-type resistor is due mainly toangular momentum rather than viscosity effects, to which theorifice-type restriction is particularly responsive, the vortex-typeresistor is less affected by temperature change and consequently controlsignals bearing a predetermined relation to temperature will be appliedby the control jets to the fluid beam. A differential pressure output,dependent on temperature, will thus be delivered by the amplifier.

SUMMARY This invention relates generally to the control system art andmore particularly to that branch of such art more recently becomingpopularly known as Flnidics Still more particularly, the invention isdirected to the provsion of a temperature compensating fluidic amplifierwhich may be arranged in a control system to make it less affected bytemperature change, either in ambient conditions or in the fluidemployed in the system.

Apparatus of this general type has previously been proposed, asexemplified in U.S. Pats. No. 3,314,294 to J. R. Colston and No.3,442,278 to R. S. Peterson; however, such apparatus has beenobjectionable since certain parts thereof required extremely smallcross-sectional flow areas and/or long passage lengths. The reduced flowareas make the components susceptible to failure due to contamination ofthe working fluid, while the use of long passage lengths presentspackaging problems and prevents the use of the components in small orcompact quarters.

An object of the invention is to provide a fluidic amplifier having theusual fluid beam for delivering fluid under pressure to a plurality ofreceivers in proportion to the forces of control jet streams applied toopposed sides of the fluid beam, the forces of the control jet streamsbeing varied in accordance with temperature change to cause theamplifier to produce a differential pressure output which is temperaturedependent, the fluidic amplifier avoiding the objections to priorstructure noted above.

An object also is toprovide a fluidic amplifier having control jetapplying means with components for creating differential pressurecontrol flows, one component being a restrictor which is affected bychanges in viscosity of the system fluid and the other being arestrictor which is relatively unaffected by such changes, thedifferential control flows thus varying in accordance with temperaturechanges producing variations in fluid viscosity.

Another object also is to provide a fluidic amplifier having control jetapplying means with a restrictor of the orifice type in communicationwith one control jet and a restrictor of the vortex type communicatingwith the other control jet, since the resistance of the vortex-typerestric- Mice tor is due primarily to angular momentum of the fluidrather than viscosity effects, it varies less with absolute temperaturechange than the resistance of the orifice-type restrictor and a controlpressure differential which varies as a function of temperature isproduced, the result is an amplified temperature-dependent differentialoutput.

A further object of the invention is to 'vary the sensitivity totemperature change by placing an orifice-type resistor in parallel withthe control jet port which is in communication with the vortex-typeresistor.

Another object is to vary the sensitivity of the device to temperaturechange by placing a shunt resistance across the output passages of theamplifier, or by placing degaining orifices in the output passages.

A further object is to change the Vortex dimensions to vary thesensitivity of the device to temperature change.

The foregoing and other objects may be secured with various forms ofstructure schematically illustrated in the accompanying drawing anddescribed hereinafter.

THE DRAWINGS FIG. 1 is a schematic View of a temperature compensatingfluidic circuit embodying the present invention;

FIGS. 2, 3 and 4 are schematic views of the structure or parts thereofmodified to increase the sensitivity of the circuit shown in FIG. l; and

FIG. 5 is a graph showing the results of tests of various forms of theinvention.

Referring more particularly to the drawing, and especially FIG. 1, thecircuit shown therein includes a conventional proportional amplifier 10.While a proportional amplifier has been illustrated, it should beunderstood at this point that the principles of the invention areequally applicable to a digital amplifier. The amplifier 10 includes aninteraction chamber 11, having a beam-forming inlet nozzle 12 at oneside and a pair of output passages 13 and 14 at the opposite side. Thechamber is also provided with a pair of control jet nozzles 15 and 16,these being arranged between the nozzle 12 and the output passages atopposite sides of the nozzle 12. The latter is adapted to receive fluidunder pressure from a source 17 and direct a fluid beam 18 generallytoward the output passages 13, 14. The beam 18 is controlled by theapplication of fluid pressures to either side thereof through thenozzles 15 and 16, the quantity of fluid received by the output passages13 and 14 being in proportion to the difference in forces of the controlstreams issuing from the jets 15 and 16. These jets are connected bypassages 20 and 21 with a source of control pressure which may be eitherthe source 17 or other suitable source.

The forces of the control jets in the present instance are varied byincorporating restrictions in the passages 20 and 21. Passage 20 isprovided with a restriction 22 of the orifice type and passage 21 isprovided with one or more restrictions 23, 23a, the resistance of whichis due to angular momentum of the fluid flowing through the passage 21.Since resistance, which is due to angular momentum, is less affected byvariations in the Viscosity of the fluid flowing through therestrictions, the resistance offered by restrictors 22 and Z3 willdiffer at different temperatures. By reason of this difference, controlpressure signals due to temperature change will be applied to the beam18 and will cause a differential pressure output in passages 13 and 14dependent on temperature. The forces of the pressure output signals willbe increased due to the natural action of the amplifier 10.

One form of resistor of the angular momentum type is a vortex resistor,schematically illustrated at 23. Such a resistor comprises a circularchamber 24 into which fluid is introduced tangentially, as at 25,through passage branch 21a. An outlet port 26 leads from the centerportion of the chamber 24 via passage branch 2lb to passage 21.

Fluid flowing through branch 21a swirls around in chamber 24 and exitsthrough outlet port and branch 2lb to passage 21. The resistance to liowoffered by the vortextype resistor will be substantially the sameregardless of any change in viscosity due to temperature change. Theresistance offered by the restrictor 22, however, will vary with changesin viscosity of the fluid and, as previously mentioned, the forcesapplied to beam 18 by jets 15 and 16 will differ as temperature changes.A single vortextype resistor could be employed. It is desirable,however, to utilize a plurality of such resistors 23, 23a to permit theuse of an orifice-type resistor in line 20 of a size which will berelatively immune to contamination of the fluid. The vortex-typeresistors 23, 23a are arranged in parallel as shown in FIG. 1.Sensitivity of the control to variations in temperature may be increasedby connecting an orifice-type restriction 27 to passage 21 on thedownstream side of the vortex resistors, restrictor 27 venting to theambient atmosphere.

Use of resistor at 27 discharging to ambient increases the flow throughthe vortex resistors and thus increases the swirl strength therein. Thesensitivity of the amplifier may be varied in a number of differentways. For example, FIG. 2 schematically illustrates a change indimensions of the vortex resistors 30 and 31. In FIG. 2, resistor 30 isrepresented as having a smaller diameter chamber than resistor 31. Otherdimensions, such as the depth of the chamber, may be varied with similarresults.

In FIG. 3, a shunt resistance is applied across the output passages 13,14. In FIG. 4, each passage 13a, 14a is provided with a de-gainingorifice 32.

In the graph of FIG. 5, there are shown the results of tests ofamplifiers with different sensitivity adjusting means. The traces A, B,C, D1, D2, and D3 show that the variation in differential output of theamplifier due to temperature change is linear. In this graph the curvesshow differential pressure changes in the output of the amplifier withdifferent size restrictions at 27. Curve A indicates the output pressuredifferential with an orifice 27 of a selected size. Curve B shows theresults of the use of an orifice 27 twice as large, and Curve C resultsfrom an orifice three times -as large. Curves D1, D2 and D3 result fromthe use of orice 27 of the selected size in combination with varioussize de-gaining orices in the output passages.

It should be obvious that, as indicated, the restrictions of the orificetype could also be made adjustable, if desired or found advisable.

I claim:

1. Temperature compensating fluidic circuit means comprising:

(a) an amplifier having means forming an interaction chamber with abeam-forming inlet nozzle at one side, spaced output passages at theopposite side, and a control jet nozzle at either side of said inletnozzle, said inlet nozzle being adapted to receive fiuid under pressurefrom a supply source;

(b) a first passage with viscosity sensitive resistance means leadingfrom a control pressure source to one of said control jet nozzles; and

-(c) a second passage with resistance means of a vortex type leadingfrom said control pressure source to the other of said control jetnozzles.

2. Temperature compensating fiuidic circuit means oi claim 1 in which ashunt resistance across the output passages is provided to vary thesensitivity of the amplifier means.

3. Temperature compensating uidic circuit means of claim 1 in whichpredetermined dimensions of the vortex type resistance means is variedto adjust the sensitivity of the amplifier means.

4. Temperature compensating liuidic circuit means of claim 1 in whichthe output passages are provided with adjustable de-gaining orifices tovary the sensitivity of the amplifier.

5. Temperature compensating fluidic circuit means of claim 1 in whichthe second passage is provided with a plurality of resistance means ofthe vortex type.

6. Temperature compensating fluidic circuit means of claim 5 in whichthe resistance means in said second passage are arranged in parallel.

7. Temperature compensating fluidic circuit means of claim 1 in whichthe second passage has an oriiice discharging to ambient in parallelwith said other control jet.

8. Temperature compensating uidic circuit means of claim 7 in which theorifice discharging to ambient is adjustable.

References Cited UNITED STATES PATENTS 3,587,602 6/1971 Urbanosky137-815 3,587,606 6/1971 Howland 137-815 3,587,616 6/1971 Boothe 137-8153,598,137 8/1971 Glaze 137-815 3,603,334 9/1971 Davies et al IS7-81.53,442,278 5/1969 Petersen 137-815 3,529,614 9/1970 Nelson 137-8153,557,810 1/1971 Lomas 137-815 3,250,469 5/1966 Colston 132-8153,536,085 10/1970 Taplin 137-815 3,570,511 3/1971 Bermel 137-81.5

SAMUEL SCOTT, Primary Examiner

